Sputtering processes are employed to deposit thin films onto substrates to manufacture any of a variety of devices. Sputtering processes typically involve bombarding a solid sputtering target body with energized particles to eject atoms from the target body.
Sputtering targets may be made by ingot metallurgy, pursuant to which an ingot is formed (e.g., by electron beam melting of a metal), and thereafter thermomechanically processed for achieving a desired texture. Sputtering targets also may be made from powder metal starting materials, which are suitably consolidated to form a resulting target. When powder metals are used as starting materials it is typically desirable to employ high purity powders. For example, it is desired to employ powders that have a low content of undesired metallic impurities, and/or a low content of oxygen.
It has been recognized that sputtering target bodies having generally uniform crystallographic texture tend to enhance the ability to obtain uniformity in the resulting films.
There is an ongoing need for alternative sputtering targets, and particularly sputtering target bodies that exhibit a crystallographic texture that approximates theoretically “random crystallographic texture.” As the skilled artisan would appreciate, a “random crystallographic texture” is a texture that is free of any preferred crystallographic orientation due to processing history (e.g., plastic deformation) over at least 95% of its volume (such as artifacts of a thermomechanical processing of a target body), such that distribution of grain orientations can be thus regarded as isotropic and occurring in a random statistical manner. There is especially a need for alternative tantalum-containing sputtering target bodies (such as target bodies prepared from powdered tantalum) that exhibit random crystallographic texture and that avoid the need for costly and energy intensive thermomechanical processing steps.
Examples of efforts to provide tantalum-containing sputtering targets are illustrated in one or more of U.S. Pat. Nos. 6,521,173; 6,261,337; 5,580,516; 7,601,296; 6,589,311; 6,770,154; 7,081,148; and published United States Patent Application 20090038362 (all of which are hereby expressly incorporated by reference). Also of potential relevance to the present teachings are published United States Patent Application Nos. 20040016635 and 20070243095, both incorporated by reference.
In U.S. Pat. Nos. 6,521,173 and 6,261,337, there is disclosed an approach for preparing powders having relatively low oxygen content. See also U.S. Pat. No. 8,226,741 and published U.S. Patent Application 20080078268 (incorporated by reference). Also disclosed are methods that contemplate consolidation by hot isostatic pressing of the powders. In published United States Patent Application No. 20090038362, which discusses U.S. Pat. No. 6,521,173 (see paragraph 12), there is disclosed an approach to controlling crystallographic texture by asymmetric rolling.